... some other apeiron nature, from which come into being all the heavens and the worlds in them. And the source of coming-to-be for existing things is that into which destruction, too, happens, according to necessity; for they pay penalty and retribution to each other for their injustice according to the assessment of Time', as he describes it in these rather poetical terms.

Their commentary on the excerpt begins:

Simplicius is undoubtedly quoting from a version of Theophrastus' history of earlier philosophy, and from the section on the material principle, περὶ ἀρχῆς. The concluding clause, a judgement on Anaximander's style, shows that what immediately precedes is a direct quotation. Thus κατὰ τὴν τοῦ χρόνου τάξιν, which many have held to be a Theophrastean paraphrase of κατὰ τὸ χρεών, should provisionally be accepted as original. διδόναι -- ἀδικίας is certainly original, and well exemplifies the poetical style noted by Theophrastus. κατὰ τὸ χρεών, too, should probably be accepted as by Anaximander: χρεών retained a marked poetical colouring (except in the special usage χρεών ἐστι) until the expression τὸ χρεών became popular in the Hellenistic period as a circumlocution for death...

So far so good; and the contrast between 'certainly' on the one hand, and 'provisionally' and 'probably' on the other, suggests reasoning by likelihoods. It's the remainder of the argument that worries me:

The preceding words, ἐξ ὧν -- εἰς ταῦτα γίνεσθαι, have been much disputed. The use of the abstracts γένεσις and φθορά, well established in Peripatetic but not (from the other extant evidence) in Presocratic vocabulary, suggests that these belong to Theophrastus.

But although KRS use the word 'suggests', their argument seems too weak to yield a likelihood.

After all, we concede that Anaximander coined a strange word, ἄπειρον; we do not hesitate to consider that he might have taken a common word, ἀρχή, and used it with a new and technical sense; γένεσις and φθορά were not themselves technical terms over which Peripatetics had a proprietary claim; and Plato (not a Peripatetic) in referring back to early Greek natural philosophy uses the phrase, περὶ γενέσεως καὶ φθορᾶς, as if this were an already well-established usage then. All of these things and more would need to be evaluated to establish a likelihood.

In short, it seems that this argument alone can 'suggest' something only if the Cartesian Canon is implicitly in force.

Next KRS continue:

The sentiment, too, looks Peripatetic: it is a close restatement of one of Aristotle's basic dogmas about the primary substance of the physical monists, 'all things are destroyed into that from which they came-to-be' (Phys. III.5, 204b33, ...).

Of course it's possible, too, that Anaximander actually said something along the lines of that which Aristotle ascribed to him! KRS' remark can establish only the possibility that the sentence is a Peripatetic interpretation rather than a quotation. It does nothing to establish a likelihood. (Oddly KRS later, on pp. 121-22, propose that ἐξ ὧν -- εἰς ταῦτα γίνεσθαι is a Theophrastean paraphrase of something that Anaximander actually said. But one can't have it both ways: the clause either conveys Anaximander's 'sentiment' or it does not.)

KRS next add, by way of conclusion:

Theophrastus was given to quoting single words or phrases; thus, he could have quoted the concluding phrase of a sentence, the rest of which he had paraphrased, in order to emphasize the connexion with the following sentence which he quotes in full.

Indeed he could have done so. But similarly he could have quoted an entire sentence. Again, no likelihood is established by this argument (which is masked by the phrase, 'given to').

What would be relevant here, to establish a likelihood, is something like the following: In cases in which Theophrastus quotes an entire sentence, it is more likely than not that he introduces that quotation by leading in with a fragment of a preceding sentence; moreover, he is disposed to do so even when what is contained in that fragment is essentially repeated in the wholly quoted sentence (as in κατὰ τὸ χρεών / κατὰ τὴν τοῦ χρόνου τάξιν).